U.S. Pat. No. 4,503,188 describes the preparation of star-block polymers by reaction of anionically polymerized polymer segments with a multiester having the formula (CH.sub.2 .dbd.CH--CO--O--).sub.n --X wherein X is the residue of a polyhydroxyl compound having n hydroxyl groups, and n is from 2 to 6. The anionically polymerized polymer segments such as a linear polybutadiene are essentially copolymerized with the unsaturation of the multiester to give a star structure having --CO--O-- groups at the core of the star polymer.
U.S. Pat. No. 4,075,186 describes the preparation of branched polymers having from 25% to 75% by weight of a linear backbone of a polyacrylate following reaction of the polyacrylate with anionically polymerized polymer segments such as a linear polybutadiene. The polymer backbone has pendent --CO--OR groups that are partially consumed in the grafting reaction wherein R is a hydrocarbon radical having from 1 to 30 carbon atoms. The polyacrylate backbone has a minimum number average molecular weight of 10,000.